1. Field of the Invention
The present invention relates to disc drives, and in particular to a head and gimbal assembly having a small thickness to thereby allow a small spacing between hard discs in a disc drive.
2. Description of Related Art
Conventional disc drives for use in work stations, personal computers, and portable computers are required to provide a large amount of data storage within a minimum physical space. In general. Winchester-type disc drives operate by transferring data between read/write transducing heads and one or more rotating magnetic storage discs. Positioning of the heads at the desired location over respective data tracks on the discs is accomplished by an actuator assembly coupled to control electronics. The electronics control rotation of the discs, positioning of the actuator assembly and the read/write functions of the heads.
Greater demands are being placed on disc drives by (1) the use of multi-user and/or multi-tasking operating systems, (2) work stations which provide an operating environment requiring the transfer of large amounts of data to and from a hard disc and/or large numbers of disc accesses to support large application programs or multiple users, (3) the present popularity of notebook and laptop computers, and (4) the continuing trend toward higher performance microprocessors. All such systems require a hard drive having high-capacity storage capability, while occupying a minimum of space within the host computer. In order to accommodate these demands, there is a need to produce a smaller hard disc drive which at the same time has an increased storage capacity. For such applications, single drive capacities on the order of several gigabytes are common.
An important determinant in the storage capacity of a disc drive is the flying height of the transducing heads above the rotating disc. Read/write transducing heads are typically mounted in a head slider. In conventional Winchester-type hard drives, once the storage disc achieves a certain angular velocity after start-up of the drive, a cushion of circulating air above the surface of the disc forces the head slider and read/write head up off the surface of the disc to thereby achieve a flying height. As long as the disc maintains a certain minimal rotational velocity, the head slider rides on this cushion of air above the disc surface. Having very low flying heights offers several advantages, primary among them is that flying the head very close to the disc surface allows for a high data bit density (i.e, the number of data bits per inch on a data track). The greatest data bit density would be obtained where the transducing head rides in contact with the storage disc. However, the contact of the head and head slider with the disc surface would result in damage to the head and/or disc in an unreasonably short period of time. Thus, there has been an industry wide push to decrease the height at which read/write heads are maintained over the disc surface without actually riding in contact with the disc surface. In the 1960""s flying heights were commonly about 100 microinches (xcexcxe2x80x3). At present, technological advances in read/write heads and disc drive design have allowed the reduction of flying heights to around 1 xcexcxe2x80x3 in commercially viable disc drives.
FIG. 1 shows a conventional actuator assembly 10 for supporting read/write heads 12 with respect to discs 14. In particular, heads 12 are supported on flexures 16, which are in turn mounted on load beams 18. The load beams 18 are attached to an actuator arm 20, which is attached to a voice coil motor (not shown) for pivoting the actuator assembly about an axis 19 to position the heads 12 over the desired data tracks on the discs 14. The load beams 18 in conventional actuators are provided to exert a force or load to bias the heads 12 toward the surfaces of discs 14. During operation of the drive, the force of the load beams 18 oppose and counteract the force of the cushion of air under the sliders so that the heads reach an equilibrium state at the desired flying height.
It is an important function of flexures 16 to provide a gimbaling action which allows the heads 12 to fly flat over the discs, i.e, to orient the surface of the heads 12 so that they are generally parallel to the discs while the discs are rotating. Toward this end, flexures 16 typically include a tongue provided at an angle with respect to the main body of flexure. The angle of the tongue with respect to the flexure is provided to compensate for the angle that the load beam 18 forms with respect to the disc surface. When heads 12 are mounted to the flexure tongue, the heads 12 are generally parallel to the surface of the discs 14.
Even as 2xc2xd inch form factor disc drives were introduced in the market place in the early 1990s, disc drive manufacturers were in the process of designing a 1.8 inch form factor disc drive. However, owing in part to the large memory requirements of Windows(copyright)-based applications, 1.8 inch form factor disc drives have not yet gained wide spread acceptance, as these drives have conventionally not had sufficient hard disc storage capacities to meet customer demands. One limitation to the storage capacities of 1.8 inch form factor disc drives, and disc drives in general, is that the above-described configuration of conventional actuator assemblies requires a minimum spacing (Smm in FIG. 1) between adjacent hard discs. This distance in conventional 1.8 inch form factor drives is approximately 60 to 80 mils. A smaller spacing between the discs would not leave sufficient room for the load beams, flexures and heads to fit in between adjacent discs.
Industry standards have dictated general dimensions for particular drive form factors. For example, the height of 1.8 inch form factor drives is generally no more than about 0.25 inches. It would of course be advantageous to fit more hard discs within a particular form factor to thereby increase the drive storage capacity. However, the disc spacing necessitated by conventional actuator assemblies has been a significant limitation in the number of discs which may be placed within a particular form factor disc drive.
It is therefore an advantage of the present invention to provide an actuator assembly capable of providing read/write transducing heads on juxtaposed surfaces of adjacent discs so that the discs may be located a small distance from each other.
It is a further advantage of the present invention to increase the number of hard discs which may be located within a disc drive without increasing the height of the disc drive.
It is another advantage of the present invention to provide a suspension having a zero or near zero gram loading of the heads against the hard discs.
It is a still further advantage of the present invention to reduce the number of head suspension components, and to simplify the fabrication process, in comparison to conventional actuators.
It is another advantage of the present invention to reduce the potential for shock damage to the heads in comparison to conventional actuators.
It is a still further advantage of the present invention to reduce the potential for a head slider to disadvantageously rotate about a longitudinal axis of the slider while the head is flying above a rotating disc.
These and other advantages are provided by the present invention which in preferred embodiments relates to disc drive including a novel head and gimbal assembly (xe2x80x9cHGAxe2x80x9d) for supporting a pair of read/write heads at a desired fly height above a pair of adjacent discs. The HGA includes a rigid support arm, and a pair of thin, sheet metal suspensions mounted on opposed surfaces of the support arm. An end of each of the suspensions extends beyond an end of the support arm. These overhanging end portions include cutout sections defining a pair of back-to-back gimbals on which the read/write heads may be mounted. The suspensions may additionally include electrical connectors etched into the surface for transferring electrical signals between the read/write heads and the control electronics of the disc drive.
In operation, a single HGA may be located between two adjacent discs, so that one of the heads on the HGA performs read/write operations on one of the two adjacent discs, and the other of the heads performs read/write operations on the other of the two adjacent discs. The HGA preferably supports the heads so that they exert little or no force against the discs. This allows the load beam found in conventional actuator suspensions to be omitted from the present invention. Upon rotation of the discs, the suspensions flex slightly as necessary so as to support the heads on an air bearing at a desired flying height.